Acetabular cup assembly for multiple bearing materials

Abstract

A modular acetabular cup assembly for use with multiple bearing liners is disclosed. The acetabular cup assembly includes a shell having a tapered inner wall and two circumferential grooves. The shell may be used with polyethylene, ceramic, metal, and other types of liners.

What is claimed is: 
     
       1. An acetabular cup system, comprising:
 a shell having a generally concave inner surface, an outer surface, an end face formed at an upper end of the shell, an apex formed at a lower end of the shell along a curved portion of the inner surface, and a central axis extending through the apex, wherein the inner surface comprises a plurality of scallops positioned adjacent the end face, a tapered wall extending from the scallops toward the apex, a protrusion inwardly extending away from an adjacent portion of a segment of the inner surface that is located below the tapered wall, and a groove that extends from the protrusion to the curved portion of the inner surface;
 wherein the shell is configured to receive each of a plurality of liners, the plurality of liners including:
 a polymer liner comprising a plurality of tabs sized and shaped to be received in the scallops, and a bump sized and shaped to be received in the groove; and 
 a metal liner comprising a tapered outer surface; 
 
 wherein, when the polymer liner is seated in the shell, each tab is received in a corresponding one of the scallops, the bump is received in the groove, and an interference fit is formed between the polymer liner and the shell, the interference fit including engagement of the bump with the groove; 
 wherein, when the metal liner is seated in the shell, the tapered wall is engaged with the tapered outer surface to thereby retain the metal liner in the shell; and 
 wherein the curved portion of the inner surface has a curved cross-section along a plane including the central axis. 
 
 
     
     
       2. The system of  claim 1 , wherein the polymer liner is formed of a polymeric material including at least one of cross-linked polyethylene and conventional polyethylene. 
     
     
       3. The system of  claim 1 , wherein the tapered wall forms an angle of about 18° with respect to the central axis. 
     
     
       4. The system of  claim 1 , wherein the bump is a lower bump, wherein the groove is a lower groove, wherein the shell further comprises an upper groove located between the tapered wall and the protrusion, and wherein the polymer liner further comprises an upper bump sized and shaped to be received in the upper groove, and wherein the protrusion defines a lower wall of the upper groove and an upper wall of the lower groove. 
     
     
       5. The system of  claim 4 , wherein a line extends from a first location at which the inner surface meets the lower groove to a second location at which the central axis meets a plane defined along the end face of the shell, and wherein the central axis and the line define an angle in the range of 40° to 70°. 
     
     
       6. The system of  claim 5 , wherein a distance between the upper groove and the lower groove is between two millimeters and four millimeters. 
     
     
       7. The system of  claim 1 , wherein the shell is further configured to receive a ceramic liner comprising a second tapered outer surface, and wherein, when the ceramic liner is seated in the shell, the tapered wall is engaged with the tapered outer surface to thereby retain the ceramic liner in the shell. 
     
     
       8. The system of  claim 1 , wherein the shell further includes an outwardly extending circumferential recess, and wherein the recess is positioned beneath a portion of the end face and extending through the plurality of scallops. 
     
     
       9. The system of  claim 1 , wherein the shell further includes a notch in a portion of the end face, and wherein the notch extends between the inner surface and the exterior surface of the shell. 
     
     
       10. The system of  claim 1 , wherein the plurality of scallops are inwardly-facing and oriented toward the central axis of the shell. 
     
     
       11. The system of  claim 1 , wherein a portion of the metal liner is coupled to an outer body that includes at least one body bump, and wherein, when the metal liner is seated in the shell, the at least one body bump engages the groove. 
     
     
       12. The system of  claim 11 , wherein the outer body that is coupled to the metal liner is formed from a material that is different than the material of the metal liner. 
     
     
       13. The system of  claim 1 , wherein the groove is non-continuous about the inner surface of the shell. 
     
     
       14. The system of  claim 1 , wherein at least a portion of the inner surface is highly polished to reduce generation of debris from engagement with the polymer liner. 
     
     
       15. The system of  claim 1 , wherein the at least a portion of the inner surface that is polished has an average surface roughness of between 1 microinch and 16 microinches. 
     
     
       16. An acetabular cup system, comprising:
 a shell having a generally concave inner surface, an outer surface, an end face formed at an upper end of the shell therefor along a curved portion of the inner surface, and a central axis extending through the apex, and an apex positioned at a lower end of the shell, wherein the inner surface comprises:
 a plurality of inwardly-facing scallops positioned adjacent the end face; 
 a tapered wall extending from the plurality of inwardly-facing scallops toward the apex; 
 a first groove and a second groove, the first groove and the second groove both positioned below the tapered surface; and 
 a protrusion positioned between the first groove and the second groove, the protrusion being generally defined by a first wall and a second wall, the first wall further defining a portion of the first groove, the second wall further defining a portion of the second groove, the second groove extending to a curved portion of the inner surface, the curved portion of the inner surface having a curved cross-section along a plane including the central axis; 
 
 wherein the shell is configured to receive each of a plurality of liners, the plurality of liners including:
 a polymer liner comprising a plurality of tabs sized and shaped to be received in the scallops, and a first bump sized and shaped to be received in the first groove and a second bump configured to be received in the second groove; and 
 a metal liner comprising a tapered outer surface; 
 
 wherein, when the polymer liner is seated in the shell, each tab is received in a corresponding one of the scallops, the first bump is received in the first groove, the second bump is received in the second groove, and an interference fit is formed between the polymer liner and the shell, the interference fit including engagement of the first bump with the first groove and engagement of the second bump with the second groove; and 
 wherein, when the metal liner is seated in the shell, the tapered wall is engaged with the tapered outer surface to thereby retain the metal liner in the shell. 
 
     
     
       17. The system of  claim 16 , wherein a portion of the metal liner is coupled to an outer body that is formed from a material that is different from the material of the metal liner, wherein the outer body includes at least a first body bump and a second body bump, wherein the first body bump positioned for engagement with the first groove, and wherein the second body bump is positioned for engagement with the second groove. 
     
     
       18. The system of  claim 16 , wherein the polymer liner is formed of a polymeric material including at least one of cross-linked polyethylene and conventional polyethylene. 
     
     
       19. The system of  claim 16 , wherein the shell further includes an outwardly extending circumferential recess, and wherein the recess is positioned beneath a portion of the end face and extending through the plurality of scallops. 
     
     
       20. The system of  claim 16 , wherein the shell further includes a notch in a portion of the end face, and wherein the notch extends between the inner surface and the exterior surface of the shell.